Question

find the limit of (sqrt(x+5)-4)/(x-11) as x approaches 11

Answer 1

$\lim\limits_{x\to11}\dfrac{\sqrt{x+5}-4}{x-11}=\lim\limits_{x\to11}\dfrac{(\sqrt{x+5}-4)(\sqrt{x+5}+4)}{(x-11)(\sqrt{x+5}+4)}\\\\=\lim\limits_{x\to11}\dfrac{(\sqrt{x+5})^2-4^2}{(x-11)(\sqrt{x+5}+4)}=\lim\limits_{x\to11}\dfrac{x+5-16}{(x-11)(\sqrt{x+5}+4)}\\\\=\lim\limits_{x\to11}\dfrac{x-11}{(x-11)(\sqrt{x+5}+4)}=\lim\limits_{x\to11}\dfrac{1}{\sqrt{x+5}+4}=\dfrac{1}{\sqrt{11+5}+4}\\\\=\dfrac{1}{\sqrt{16}+4}=\dfrac{1}{4+4}=\dfrac{1}{8}\\\\Answer:\ d.\ \dfrac{1}{8}$